Sola Sound Hybrid GE-SI Tone Bender MKII

[Blues1911]

Hello, for everyone that loves Tone Bender MKII, here's some new stuff from Sola Sound that can maybe help avoiding the germanium instability, at least for a good measure.

I've drawn the layout (which is the same of the classic layout) according to the photos I've found here and there. It shows with some bias resistors changed and some corrections on the frequency cut for compensate the silicon brighness.

More info at http://www.macaris.co.uk/pro-mkii-toneb ... id/p/p4181

Q1 is a germanium AC127 (supposedly quite leaky), no info around Q2 and Q3, but I guess that any low gain transistor will be useful.

Nothing fancy, apparently.

The small layout wasn't draw by me. Both are NOT verified, at least by me, but hopefully I will solder something pretty soon.

Any update or correction is warmly welcome. I should also post an exhaustive schematic, soon.

[EmmG]

I built it last year from here, where you got the layout:
http://dirtboxlayouts.blogspot.com/2019 ... ybrid.html

It's a small TBmk2 run mentioned on the DAM forum where Q2 &Q3 are low gain silicon, yet Q1 remains germanium, so it cleans up as you would expect. The goal was a lower cost model that keeps the germanium feel. It's an easy build that sounds great.

[Manfred]

It's a small TBmk2 run mentioned on the DAM forum where Q2 &Q3 are low gain silicon, yet Q1 remains germanium, so it cleans up as you would expect. The goal was a lower cost model that keeps the germanium feel. It's an easy build that sounds great.

What types of transistors were used?

[EmmG]

No information on that yet, All the low gain ones I've used have sounded good.

[Blues1911]

What types of transistors were used?

I don't think the type really matters. Unlike germanium, silicon transistors are extremely consistent, should be built in a very standardized way, show no leakage at all and generally all sound pretty much the same, provided they have the same hfe. Think about Silicon Fuzz Face: if you select transistor with more or less the same hfe, they hardly sound different.

Just select some silicon transistor with low hfe, in the range of 70-150, and they should fit perfectly.

[Blues1911]

I built it last year from here, where you got the layout:
http://dirtboxlayouts.blogspot.com/2019 ... ybrid.html

It's a small TBmk2 run mentioned on the DAM forum where Q2 &Q3 are low gain silicon, yet Q1 remains germanium, so it cleans up as you would expect. The goal was a lower cost model that keeps the germanium feel. It's an easy build that sounds great.

Can you share the parameters of the germanium transistor you've used for Q1? Of course the type, but most important hfe and especially hfe, which seems crucial in the Tone Bender MKII circuit.

[Blues1911]

I built it last year from here, where you got the layout:
http://dirtboxlayouts.blogspot.com/2019 ... ybrid.html

It's a small TBmk2 run mentioned on the DAM forum where Q2 &Q3 are low gain silicon, yet Q1 remains germanium, so it cleans up as you would expect. The goal was a lower cost model that keeps the germanium feel. It's an easy build that sounds great.

Can you share the parameters of the germanium transistor you've used for Q1? Of course the type, but most important hfe and especially hfe, which seems crucial in the Tone Bender MKII circuit.

* especially leakage. Sorry.

[audiohub]

This is all really great info! Thanks so much.

Has there been an actual schematic posted anywhere yet?

Construction on this looks top-notch as is all Macari/DAM stuff.
Love the textured blue finish as well.